Create a spider with bones and ik on the feet
and go to - Animate - Set driven keys -option box.

Set the rootjoint (or group) to be driver in translate z and the ik handles
of the feet to be driven in translate y and z.

Now key a step when Rootjoint is at 0 (feets down) and three more keys as
rootjoint moves along z axis. (Feets down, up, down to complete a step.)

Now if you drag the rootjoint the legs should make a step.
(Or rather a jump since they all are keyed the same.)

In Graph editor edit keys for the ik handles if you need and turn on
View infinity and set pre infinity and post infinity to cycle with offset.

Now do the same with root joint as driver in translate x axis and the ik handles translate y and x to make a sidestep.

Now you can offset the legs so they match the spider walkcycle info at www.hash.com/users/threechickens/Spider.htmTo make it easier to use the spider leg offset chart move the spider the same distance as the number of frames in the chart. I.e 0.12, 1.2, or 12 depending on your scale.
I made the mistake of making the step 0.15 and had to recalculate the offset to get it right.

One note. Its important that the step is exactly the same lenght as the distance the rootjoint moves.

Thats it! The good thing with this is its working in realtime in the viewport so you get instant feedback.
Ctrl click the y axis to constrain movement in only x and z axis and start crawling around. Good luck!